Method of making microporous polyolefin articles and product therefrom



United States Patent METHOD OF MAKING MICROPOROUS POLY- OLEFIN ARTICLES AND PRODUCT THERE- FROM Peter J. Canterino, Clifton, N.J., and Lewis V. Fonts, Bartlesville, Okla assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed May 16, 1961, Ser. No. 110,362

6 Claims. (Cl. 260-25) This invention relates to modified polyolefin compositions and to the production of microporous thermoplastic articles. In accordance with one aspect, this invention relates to the plasticization of modified solid monoolefin polymers. In accordance with another aspect, this invention relates to the production of microporous articles from plasticized modified solid monoolefin polymers.

In recent years, many different types of polymers have been developed and are now in wide scale commercial use. Also, various polymerization processes have been developed for the manufacture of high density polyolefins such as polyethylene, polypropylene, as well as copolymers of ethylene with higher monoolefins in the presence of various catalyst systems. It is well recognized in the art that the high density polyolefins are extremely difficult to plasticize. Although certain plasticizers are compatible with such polymers in the molten state, the polymer tends to crystallize out on solidifying and exudes the plasticizer. Thus, if one could satisfactorily plasticize such polymers in a manner so that the plasticizer is maintained within the solid polymer, compositions would then be available having greater extrudability for the formation of films and other molded articles. g

Also, the high density polyolefins have found wide utility in the molding art and thus formed into such items as dishes, bottles, films and the like; also these polymers are useful in many applications to prevent the transmission of water vapor since these polymers have very low permeabilities. However, on the other hand, if one could form porous materials or articles from such polyolefins, even broader fields of application for such materials would be available.

This invention provides a novel plasticized polyolefin composition, a novel porous polyolefin composition, and a method of production thereof.

Accordingly, an object of this invention is to provide plasticized thermoplastic polymeric compositions comprising modified monoolefin polymers.

Another object of this invention is to provide polyolefin compositions of high extrudability.

Another object is to provide a method of plasticizing modified solid monoolefin polymer compositions.

A further object of this invention is to provide a method for forming porous articles from polyolefins.

A stillfurther object of this invention is to provide porous, paper-like products from polyolefins.

Other aspects, objects and the several advantages of the invention are apparent from a study of the disclosure and the appended claims.

According to the invention, a polyolefin composition having improved extrudability and molding properties, i.e., substantially a non-bleeding composition, is obtained by blending a polyolefin resin, that has been modified by reacting it with a suitable polymerizable vinylidene monomer under polymerization conditions, with a minor proportion, sufiicient to plasticize said polyolefin, of a plasticizing material such as a material selected from the highboiling esters, and high-boiling polymers.

Further, according to the invention, novel porous polyolefin products are prepared by contacting a plasticized modified polyolefin composition, such as set forth above,

3,228,896 Patented Jan. 11, 1966 ice after molding, with a solvent under extraction conditions such that the plasticizer as well as certain other, materials are selectively removed from the molded composition, thus leaving the porous molded material as a product of the process.

According to this invention, solid l-olefin polymers are first modified or graft polymerized by coating the polymer, preferably a high surface area form of the polymer, Witha polymerizable liquid monomer together with a polymerization catalyst, thereafter subjecting the resulting mixture to. polymerization conditions, and then admixing the reaction product with a selected plasticizer to provide a composition having improved properties. Broadly speak-- ing, solid homopolymers of l-olefins containing from 2 to 8 carbon atoms, inclusive, as well as copolymers of these l-olefins With each other can be employed according to the invention. Suitable solid monoolefin polymers that can be employed include the high density and the low density polyethylenes, polypropylene, ethylene-propylene copolymers, ethylene-l-butene copolymers, and the like.

The polyolefins or l-olefin polymers that can be modified and subsequently plasticized according to the invention can be prepared by any of the well-known methods which are usually employed in the preparation of these polymers. One well known method for preparing polymers of l-olefins is the chromium oxide-catalyzed polymerization described in the Hogan et al. patent, US. 2,825,- 721 (1958). The polyolefins prepared by Hogan et al, are characterized by their high density, and polymers of ethylene including homopolymers and copolymers prepared by this method generally having a density ranging from 0.920 to 0.990, ordinarily 0.930 to 0.970. i In addition to the foregoing method of preparing the l olefin polymers, especially polymers of ethylene, the invention also includes within its scope the modification and subsequent plasticization of polyolefins prepared by polymerization in the presence of an organometal catalyst such as trialkyl aluminum in conjunction with a titanium halide or polyolefins prepared by the high pressure polymerization processes which employ oxygen, peroxide, or other oxygen carrier as a catalyst.

The. polymerizable vinylidene monomers that can be used for modifying polyolefins or graft polymerization onto polyolefins can be defined as compounds containing a terminal vinylidene (H C=C group, which preferably have a molecular weight in excess of 40, and which are liquid under the conditions of operation. These monomers can be further defined as compounds of the general structural formula OHz=0-R I I in which R is hydrogen, chloro or alkyl groups containing from 1 to 3 carbon atoms and R is a radical selected from alkyl, aryl, alkaryl, aralkyl and cycloalkyl groups containingfrom 1 to 10 carbon atoms,

wherein R" is an alkyl, aryl, alkaryl, aralkyl, or cycloalkyl radical containing from 1-10 carbon atoms and wherein R is H or an alkyl radical containing from l-3 carbon atoms. Generally, the total carbon atoms in R-l -R is not more than 10 carbon atoms.

Typical compounds of this formula include propylene, styrene, alpha-methyl styrene, alpha-chlorostyrene, acrylic acid, methacrylic acid, acrylonitrile, methyl acrylate;

methyl methacrylate, butyl acrylate, butyl methacrylate,

vinyl acetate, l-butene, vinylpyridine, vinylquinoline, cyclohexyl methacrylate, isobutylene, methyl vinyl ether, vinyl naphthalene, vinylidene chloride, and the like. High boiling monomers such as n-decyl or cyclohexyl methacry- The polyolefins which are to be modified preferablyare in the form of a powder or porous particles or crumb in order that a high surface area is presented on which the monomer is adsorbed or coated. Polyolefins ground by a micropulverizer or similar device, for example, particles of 40 mesh to 200 mesh (US. Standard sieve), particles of polymer formed in a catalyzed process at a temperature below the solution temperature of the polyfner, sometimes referred to as particle form polymer (10-200 mesh particles-US. standard sieve), and socalled polymer flufi are suitable for use in the invention. Thus, in actual operation one or moreof the polyolefins is contacted with one or more liquid monomers of the above group in the presence of a polymerization catalyst and under conditions such that graft polymerization or surface modification of the polymer is effected. A frequently preferred method of operation comprises dissolving from 0.01 to 3.5 weight percent of the catalyst in the monomer prior to application to the polyolefin. Alternatively, the catalyst can be applied to the polyolefin prior to wetting with the monomer. The wetting step is preferably at a temperature and pressure such that the inonomer is in a liquid state.

Application of the monomer to the polyolefin can be made by any suitable means. A convenient method is to tumble the polymer in a drum as the monomer is added, continuing the tumbling until homogenous distribution is etfected. The amount of monomer used will be in the range between about 1.0 and about 100 weight percent based on the polyolefin. Also, operations should be conducted under conditions such that the monomer re= mains in the liquid phase, using pressure if necessary. Polymerization conditions will be governed bythe monomer-catalyst system used. The temperature range for' the polymerization will be in the range between '150 F. and about 300 F. When operating with vinyl monomers and a free radical catalyst, polymerization can be effected in the temperature range between and about 300 F. In any event, the temperature should be below the crystalline melting point of the polyolefin. The polymerization time will be in the range between about 0.5 minute and 100 hours.

According to the invention, at the end of the polymerization modification step, the polymeric product is admixed with a plasticizer, preferably at a temperature above the softening point of the polymer, but below the atmospheric boiling temperature of the plasticizer. Suitable plasticizing materials that can be employed according to the invention include the high-boiling esters, and high-boiling polymers. The plasticizers are preferably liquid at the temperature of incorporation 'or milling into the polymer and ordinarily have atmospheric boiling temperatures above about 350 F.

Representative specific examples of plasticizers that can be used include diisobutyl phthalate, diamyl phthalate, butyl octyl phthalate, butyl 'decyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, diethyl phthalate, n-octyl n-decyl phthalate, triphenyl phosphate, cresyl diphenyl r boils at atmospheric pressure. High density polyethylene,

phosphate, tricresyl phosphate, tri(dimethylphenyl)phosfor example, has a softening temperature of about 250 F. and therefore, the temperature 'of incorporation of plasticizer will generally range from about 250 F. to about 350 F. for such a polymer although temperatures outside this range can be used when desired.

- In the present process, blends of polyolefins or polyolefins onto which vinylidene monomers have been grafted are plasticized with one of the above-described materials. Generally, the mastication of the polymer with the plasticizer will be at a temperature such that the polyolefin is molten. Generally, the mastication will take place at a temperature ranging from 300 to about 550 F. Thus, any plasticizer should be compatible, to some degree, and should be liquid, but not boiling at the chosen mastication temperature. While superatmospheric pressure can be used to prevent evaporatiomthis would be fairly impractical.

- The reaction product obtained from the above-described polymerization reaction can be plasticized as such or, if desired, the reaction product can be subjected to solvent extraction or other suitable treatment to remove certain components of the product. The reaction product obtained from the polymerization comprises a graft copolymer of a polyolefin and a vinylidene material as defined, some vinylidene homopolymer (some vinylidene copolymer if more than one monomer present) and some polyolefin which has not reacted with the vinylidene m'onomer( s) Theamount of plasticizer incorporated into the modified polymer will generally range from about 5 to about 50 parts per parts of polymer when no filler is employed. If fillers are employed, the amount of plasticizer can be as high as 100 parts per 100 parts of modified polymer. The preferred range of plasticizer is from '10 to about 40 parts per 100 weight parts of modified polymer. The amount of filler or reinforcing agent employed will or-. dinarily range from about 10 to about 200 weight parts per 100 weight parts of modified polymer. Examples of suitable fillers or reinforcing agents that can be compounded into the polymer along with the plasticizer include clay, carbon black, silica, and the like. If pigments are to be used, only very small amounts are necessary to obtain intense coloration of the plasticized modified polymer. Y

The'plasticized modified polymers of this invention are useful as film resins, and are much more expensive than other film resins because of the extending effect obtained with the plasticizer. Modified polymeric materials which have been extended with asphalt, for example, are useful for agricultural purposes due to their black color and can be employed for covering crop fields to obtain a heat insulating efiect. These materials are also useful in building construction. Plasticized modified polymers of this invention can also be foamed, and both the foamed and unfoamed materials can be converted to fire-retardant insulating materials by incorporating therein, for example, chlorinated Waxes and antimony oxychloride. Also, according to the invention microporous polyolefin products are produced from plasticized molded modified polyolefin compositions, such as described above, or plasticized molded blends of polyolefins with vinylidene polymers, by contacting same with a suitable solvent under extraction conditions such that the plasticizer and/or the vinylidene polymer are selectively dissolved out of the molded composition, thus leaving a microporous polyolefin article as a product of the process.

The solid polymers of l-olefins that can be employed in the blends with vinylidene polymers include the high and low density polyethylenes, polypropylene, ethylene/ propylene and ethylene/l-butene copolymers, and the 6 EXAMPLE 1 A series :of runs was made in which a high density polyethylene was graft polymerized with styrene and the like, as described above. Broadly speaking, solid homo- 5 resulting graft polymer was plasticized with diisobutyl polymers and copolymers of l-olefins containing from phthalate. 2 to 8 carbon atoms can be employed. The vinylidene The polyethylene which was employed in these runs polymers that can be blended with the above-described Was prepared by a chromium oxide-catalyzed solution solid polyolefins are polymers of monomers which conpolymerization, using cyclohexane as the solvent. The tain a terminal vinylidene group and have a molecular 10 polymer had a density of 0.960 and a melt index of 1.2. weight preferably in excess of 40 such as described above. The graft polymer was prepared by placing 100 grams Following plasticization of a modified polyolefin comof the above-described polyethylene, in finely divided position, such as described above, or a blend of an unform (approximately 100 mesh), in a polyethylene bag. modified polyolefin with a vinylidene polymer, the con- Fifty grams of styrene, to which had been added 0.5 position is pressed, for example, at a temperature above gram of benzoyl peroxide, was then sprayed on the polythe softening point of the polyolefin in the composition ethylene. The resulting mixture was then placed in a to form films or other relatively thin sections. The screwcap jar, closed and placed in an oven at 158 176 F. formed material is then rapidly quenched to a temperaovernight. The temperature was then raised to 230 F. ture below the softening point of the polyolefin so as to for 2 hours to insure complete polymerization. maintain the polyolefin uniformly dispersed in the com- This graft polymer was then plasticized with various position. If quenching is not carried out as rapidly as amounts of diisobutyl phthalate. The plasticizer was possible, the molten polyolefin comes to the surface of milled in on a rubber mill and the properties of the the film and forms an impervious layer on the surface of plasticized polymer were then determined. The results the film when it is subsequently quenched or cooled. of these runs are expressed below as Table I,

Following the formation of the formed thin sections or films of plasticized polyolefin compositions, these sec- Table I tions are extracted at a temperature generally below 100 F. with a solvent, e.g., by immersion in the solvent for a period of time which will dissolve the plasticizer and n DIBP g./100,gratt 0 20 40 so so vinylidene polymer present in the composition. When polymer blends of olyolefins and vinylidene polymers are used, the vinylid ne polymers and plasticizer are extracted out PROPERTIES of the composition and only the polyolefin will remain in MI,190 C- 2.54 9. 37 45.0 Too high to run, the composition as the porous product. If graft polymers 53 23 033 38 i Q are used, the vinylidene polymer will be extracted out Elongation t t- 5 2 5 10 along with the plasticizer leaving only the graft polymer as a Porous Product 1 Diisobutylphthalate.

Representative examples of suitable solvents that can gggigjrlfrocedure E. be employed to effect this selective removal of the plasti- 40 4 AsTiVI 1363M: cizer and/or vinylidene homopolymer includes chloro- Not measured. form, toluene, benzene, and the like. The particular solvent which is chosen will depend upon whether a graft polymer or blended polymer is used, the vinylidene homo- EXAMPLE H polymer present, and the plasticizer which is used. Generally, the amount of solvent which is used will be suf- A graft polymer was prepared by the method of Exficient to completely immerse the pressed film or other ample I except that the polyolefin used was an ethylene/ shape in the solvent. The time required for the extracbutene copolymer which was prepared by a chromium tion of the thin sections will vary over relatively wide oxide-catalyzed polymerization in n-pentane at a temperaranges but will generally be within the range between ture below the solution temperature of the polymer. 0.5 minute and 1,000 hours. This so-called particle formfpolymer (10-200 mesh) The polymeric material, after extraction, is a porous, had a density of 0.95 and a melt index of 4.1 as deterpaper-like product which has wide utility. This material mined by ASTM D1235-57T, Procedure F. In this run, can be printed on and can thus be used in packaging 100 grams of the finely divided olefin copolymer was where permeability is desirable. Such material can also contacted with 50 grams of methyl acrylate in which was be used for decorative purposes such as wallpaper and dissolved 0.5 gram benzoyl peroxide. The procedure, th like, temperature and time were identical to Example I. The

A better understanding of the invention will be obgraft polymer was then plasticized with ester-type plastitained upon reference to the following illustrative excizers, after which the properties of the plasticized polyamples which are not intended, however, to be unduly 6O mers were determined. The results are expressed below limitative of the invention. as Table II.

Table II Parts Plasticizer/ Melt Shore Tensile Elongation Tensile Plasticizer parts Index, D Strength at Break Impact,

graft 190 C.3 Hardness P.s.i. Percent i ft. lbs. polymer DIOP 40 0. 2s 4s 1, 87 59. 3 TOP 40 0. 07 43 1,120 226 61.3

1 Diisooetyl phthalate.

1 Tricresyl phosphate.

3 ASIM D 1288-571, Procedure E.

6 By the method of AS'IM D 256 except that the test strips are placed on edge.

EXAMPLE III In another series of runs, styrene was graft polymerized onto high molecular weight ethylene/butene copolymer and the resulting graft polymer was plasticized with rene containing 1 gram of benzoyl peroxide were charged to a screw-cap jar. The jar was then placed in an air oven at 80 C. (176 F.) for 16 hours, after which the temperature was raised to 110 C. (230 F.) for 2 hours.

various amounts of asphalt In these runs the ethyl 5 The products from these two runs were combined and the ene/b-utene copolymer was made by the particle form yield of gmfi Polymer was 596 grams" process of Example II. The copolymer used in Run 1 Fifty the above'prepa'red t polymer and had a melt index (ASTM 1312384711 Procedure F) of 20 grams of dnsobutyl phthalate were milled together on 138, While the copolymer used in the remaining runs a rubber mill until uniform. Three grams of this mixhad a melt index by the same procedure of ture was then hot pressed at 325 F. and the film was The graft polymer was prepared by contacting 100 quenched immediately. This film was immersed in chloparts of the finely divided ethylene/butene copolymer mien; for mmutes i' z g i g film removeid with 50 parts :of styrene containing 1% by weight, based and e vent evapora o e resu tmg mammal on me styrene, of benzoyl peroxide Th6 procedure, was a White permeable film of the appearance of filter times and temperatures used were the same as in Ex- Paperamples I and IL A 2-1nch diameter disc of this material. was then out Aft the ft polymer was for d various amounts out and the permeability of this material to liquid toluof paving grade asphalt were milled in on a rubber mill, fine Was then determlned by meal1 a 1015mm Vapor and in some cases clay was added as a filler. The results cup. In this test, a sample of liqu1d toluene was placed of these tests are expressed below as Table III. in a cup and lid for the cup was fashioned out of the Table III Parts Asphalt, Melt Flexural Tensile Elongation Zero Tensile Run No. 100 parts graft Clay Index Modulus, ShoreD Strength at Break, Strength Impact polymer Filler 190 0. p.s.i. Hardness Percent Percent; 'Tiempegafoot-lb ure.

0. 27 5s 1, 530 21s 13. 52 0. 08 79, 000 48 1, 420 5 209 7. 7s 0, 07 as, 000 54 1, 170 s 214 5. 41 0. 2 50, 000 52 1, 170 27 219 7. 54 0. 79 33, 000 45 850 43 186 11. 49 0.18 1, 403 7 9. 5 a 11.05 1, 527 2 9.16 a 13. 34 40, 000 48 1, 570 477 210 6. 75 0. 15 84, 000 53 1, 080 5 215 40. 1o

1 AS'IM D1238-57T, Procedure'E.

2 ASIM D1238-57T, Procedure F.

4 By method of Thomas, Injection Molding of Plastics, Relnhold Pub In the above runs, the plasticized polymers containing above 40 parts of asphalt and no filler were somewhat tacky. Much less tendency to bleed was noted when filler was used. In control run 8, 100 parts of the ethylene/butene copolymer was blended with 60 parts of asphalt, while in control run 9, 66 parts of the ethylene/ butene copolymer, 40 parts of asphalt and 34 parts of commercial polystyrene (Dylene) were blended. Considerable bleeding was noted in both Runs 8 and 9.

EXAMPLE IV In one run, 200 grams of ethylene/ l-butene copolymer which was prepared by a chromium oxide-catalyzed polymerization was contacted with styrene and a polymerization catalyst to form a graft polymer. The polyethylene which was employed was a fluff material (approximately 100 mesh) resulting from solvent precipitation of polyethylene. The polyethylene had a density of 0.95 and a melt index of 1. 2.

In forming the graft polymer, 200 grams of polyethylene and 100 grams of styrene containing 0.25 gram benz-oyl peroxide were placed in a screw-cap jar which was then closed and placed in an air oven at 80 C. (176 F.) for 16 hours.

Fifty grams of the resulting graft polymer was then placed on a rubber mill and 20 grams of diisobutyl phthalate was milled in. The resulting polyolefin composition was then molded at 300 F. and immediately quenched with cooling-Water. The resulting film was then immersed in chloroform for 10 minutes, after which the extracted film was removed and dried. A porous, paper-like product resulted.

EXAMPLE V In each of two runs, 200 grams of the ethylene/1- butene copolymer of Example IV and 100 grams of sty- 00., Page 504 (1947).

porous product. The cup was then inverted and the rate at which the toluene seeped through the porous material was measured. The results of these runs are expressed below in the form of a table.

PERMEABILITY TO LIQUID TOLUENE Time, minutes: Grams toluene through EXAMPLE VI Two hundred grams of the graft polymer of Example V was milled with grams of diisobutyl phthalate, 50 grams of Ti0 and a trace of red pigment. The resulting composition was pressed into a film by the method of Example V, quenched immediately, and then extracted 30 minutes at room temperature with toluene. A red, permeable, paper-like material was recovered.

EXAMPLE VII One hundred grams of the ethylene/l-butene copolymer of Example IV, 25 grams of glacial methacrylic acid, 25 grams of styrene and 0.5 gram of benzoyl peroxide were charged to a screw-cap jar, and the closed jar was placed in an oven at 50 C. (122 F.). Fifty grams of the resulting graft polymer was then milled with 20 grams of diisobutyl phthalate. The resulting composition was then pressed into a film and rapidly quenched by the method of Example V. The resulting film was then extracted with toluene at room temperature for 72 hours. A permeable, paper-like film resulted.

9 EXAMPLE VIII A series of runs was carried out in which styrene was graft polymerized onto high molecular weight ethylene/ butene-l copolymer, prepared by a chromium oxide- 10 this temperature for 2 hours and 55 minutes, after which they were placed in an air oven and maintained at 70 C. (158 F.) for 12 hours. The polymer from these three jars was then combined, yielding 441 grams of polyherent viscosity 2.46. catalyzed polymerization. The graft polymers were then 5 plasticized with various materials, after which the plastitr r g i fi polynllfr cized compositions were converted to porous material t b let by extraction according to the process of this invention. i i' th 9 a The copolymer utilized in this example had the followa 0 m Wa er a eavmg 6 ex me 6 p0 which was then dr1ed in a vacuum oven at 70 C. mg properties. 10 F Ethylene/butene copolymer Volatiles 0.11 P 1 W1 ht I h t er e $1 5:

o m Gra ms v isc h s i tiy Denslfy 0-943 Extract 55 0. 44 Izod impart, ft./lbs., (no break) 10.29 Raflinfl-tfl 144 Flexural modulus 151,000 Untreated graft p y Tensile strength at yield, .s.i 3,342 Elongation percent 443 Port1ons of the untreated graft polymer, extracted and E50 hours 2 1,000 unextracted polymer were then plasticized, either alone Inherent viscosity 3J1 or blended with additional amounts of the ethylene/ 1 butene icopolymer, with dibutyl phthalate. The plasticizer P gi g :gggflfif; was blended with the polymer by milling on a rubber r mill at 350 F. Control runs with no plasticizer were In theS run 100 g a of the p y 50 grams also carried out, in which case milling was omitted. The of freshly distilled styrene and 0.5 gram of benzoyl perpolymers were then molded into -inch film by comoxide were charged to a one-quart ar. The ar was then pression molding for 60 seconds at 350 F. and 5,000 capped and heated in an oven at 70 C. (158 F) v rp.s.i. The films were quenched with cooling Water at night. The ar was then placed in an oven at 100 C. the end of the 60-second molding period. The films were (212 F.) for two hours. then extracted with chloroform for one hour at room Fifty grams of the above-prepared graft polymer, a temperature. fine granular material, was milled with 20 grams of di- The results of the runs are expressed below as Table V:

Table V Type and Amount of Polymer, Grams Grams Run No. Dibutyl Description of Untreated Extracted Raffinate Phthalate Extracted Films Copolymer Graft Graft Graft Polymer Polymer Polymer 33.5 16.5 0 Non-porous. 33.5 16.5 20 Porous. 0 Non-porous. 0 Do. 20 Porous. 6 0 Non-porous. 7 20 Slightly porous. 8-. 20 Porous.

butyl phthalate on a roll mill at 350 F. until homogeneous. This blend was labeled Sample A. Fifty grams of the graft polymer was milled with grams of white mineral oil, boiling point approximately 700 F., at 350 F. until homogeneous. This blend was labeled Sample 13.

Each of the above blends was then molded into 10 mil film at 350 F. and 5,000 p.s.i. The films were rapidly quenched with cooling water. The films were then extracted with chloroform for five minutes at room temperature. The results of these runs are expressed below at Table IV.

Table IV Molding Time, sec.

Sample- Run Remarks 5 Porous. More porous than A-l.

5 Porous, leather-like, less porous than A-l or A-Z. 60 Do.

EXAMPLE IX The slight porosity of the polymer from Run 7 is an indication that the amount of vinylidene polymer (grafted styrene) present was too low in this run.

A 1 -inch diameter disc was cut out of the inch thick, porous film from Run 5 of the above run. This disc was placed in the base of a glass column in a manner such that aspirator vacuum could be applied below the film. The time required for 100 ml. of a test fluid to pass through the fihnunder these conditions was then measured.

polystryene were formed.

In these runs, the desired amounts of copolymer and polystyrene were charged to a Banbury and milled at approximately 400 F. until homogeneous. In one run, a /25 by weight blend of copolymer/styrene was made in a broader sense. includes an alteration of the molecular structure of the polymer as well as changes not involving an alterastyrene.

11 up, while the second blend was 50/50 blended. The blends were then molded into -inch slabs at 400 and 15,000 p.s.-i., and rapid quenching with cooling water was used. The slabs were then soaked in xylene overnight at room temperature, after which the slabs were washed withchloroform and dried. The resulting material was white and flexible, with the appearance 'of white leather. The slab from the 50/50 blend passed 100 ml. of xylene in 2 minutes and 7 seconds by the test procedure of Example IX. The slab from the 75/25 blend did not pass xylene under the test procedure at water pump vacuum.

Although in chemical terminology the term modified when applied to a process involving a polymer may denote an operation in which the molecular structure of the polymer is altered, for example, by graft polymerization, in this specification and claims the term is used The term modified as used herein tion of the molecular structure and combinations to the tWO.

As will be evident to those skilled in the art, many variations and modifications of this invention can be practiced in view of the foregoing disclosure. Such variations and modifications are clearly believed to come withgroup consisting of homopolymers of monoolefins having from 2 to 8 carbon atoms per molecule and copolymers thereof with each other with a polymerizable liquid vinylidene monomer of the general structure t OH2=CR' in which R is an aryl radical containing from 6 to 10 "carbon atoms in the presence of apolymerization catalyst under polymerization conditions totform a polymeric mixture consisting essentially of'monoolefin polymer, vinylidene polymer and a graft copolymer of said vinylidene monomer and said m-onoolefinpolymer,'incorporatingin to said mixture from to about 100 weight parts of .a plasticizer and from 0 to about 200 weight parts of a filler per 100 parts of said mixture, said "plasticizer being selected from the group consisting of diisobutyl phthalate, diamyl phthalate, dibutyl phthalate, butyl octyl phthalate, butyl decyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, diethyl phthalate, -n-octyl n-decyl phthalate, triphenyl phosphate, cresyl diphenyl phosphate, (tri-dimethylphenyl) lphosphate, diphenyl o-xenyl phosphate, and tricresyl phosphate, molding said plasticized mixture into thin sections at a temperature above the softening temperature of said solid polymer, immediate ly quenching the molded mixture to a temperature below the softening temperature of said solid polymer so as to uniformly disperse said polymeric mixture in said composition, contacting said quenched material with a solvent selective for at least one of said plasticizer and said vinylidene polymer under extraction conditions such that at least one of said plasticizer and said vinylidene polymer are selectively dissolved out of said molded composition and recovering a microporous polymeric article as a product of the process.

2. The .process according to claim 1 wherein said polymer is polyethylene and said vinylidene monomer is 3. The microporous article of claim 1. 4. A process for providing molded polymeric compositions of improved processing properties which comprises contacting a solid polymer selected rfrom the group consisting of homopoly-mers of monoolefins having from 2 to 8 carbon atoms per molecule and copolymers thereof with each other with a polymerizable liquid vinylidene monomer of the general structure CH2=C-R' in which R is a radical represented by -COOR wherein R is an alkyl radical having from 1 to 10 carbon atoms in the presence of 1a polymerization catalyst under polymerization conditions to form a polymeric mixture consisting essentially of monoolefin polymer, vinylidene polymer and a graft copolymer of said vinylidene monomer and said monoolefin polymer, incorporating into said mixture from 5 to about weight parts of a plasticizer and [from 0 to 200 weight parts of a filler per 100 weight parts of said mixture, said plasticizer being selected from the group consisting of diisobutyl phthalate, diamyl phthalate, dibutyl phthalate, butyl octyl phthalate, butyl decyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, diethyl phthalate, n-octyl n-decyl phthalate, triphenyl phosphate, cresyl diphenyl phosphate, tri(dimethylphenyl) phosphate, diphenyl o-xenyl phosphate, and tricresyl phosphate, molding said plasticized mixture into thin sections at a temperature above the softening temperature of said solid polymer, immediately quenching said molded mixture to a temperature below the softening temperature of said solid polymer so as to uniformly disperse said polymeric mixture in said composition, contacting said quenched material with a solvent selective for at least one of said plasticizer and said vinylidene polymer under extraction conditions such that at least one of said plasticizer and said vinylidene polymer are selectively dissolved out of said molded composition, and recovering a microporous polymeric article as a product of the process.

5. The process according to claim 4 wherein said solid polymer polyethylene and said vinylidene mono-mer is methyl iacrylate.

6. The microporous article of claim 4.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 11/ 1948 Great Britain. 12/ 1961 Great Britain.

9/ 1958 France. 4/ 1959 France.

OTHER REFERENCES Buttrey: Plasticizers, 2nd edition, Cleaver-Hume Press Ltd., 1957, page 64.

R-aflt' et al.: Polyethylene, volume XI, Interscience Peublishers,lnc.', New York, 1956, page 239.

MURRAY TILLMAN, Primary Examiner.

LEON J. BERCOVITZ, Examiner. 

1. A PROCESS FOR PROVIDING MOLDED POLYMERIC COMPOSITIONS OF IMPROVED PROCESSING PROPERTIES WHICH COMPRISES CONTACTING A SOLID POLYMER SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYMERS OF MONOOLEFINS HAVING FROM 2 TO 8 CARBON ATOMS PER MOLECULE AND COPOLYMERS THEREOF WITH EACH OTHER WITH A POLYMERIZABLE LIQUID VINYLIDENE MONOMER OF THE GENERAL STRUCTURE 